Bathroom drains tend to require maintenance or repair a little more often than those in the kitchen. The bath has no garbage disposal and the kitchen drain doesn’t get anywhere near as much hair. The sink drain is the most likely culprit. Hand soap, toothpaste, hair and other things tend to gum it up.

A mixture of a 1/4 cup of baking soda and a cup of vinegar is an inexpensive home remedy that will unclog many plugs. It has the added advantage of removing calcium carbonate (the white chalky deposits), which opens up the pipe and clears the space between the sink flange and the stopper. If that’s not strong enough, use a commercial drain opener chemical. They’re safe for the pipes and the environment. They degrade rapidly.